Composite signaling-circuits



H. S. OSBORNE. COMPOSITE SIGNALING CIRCUITS.

APPLICATION FILED JUNE 8.1917.

' Patentvd Sept. 2, 1919.

INVEN'II'OR ATTORNEY HAROLD s. OSBORNE, on NEW YORK, N. Y.,

ASSIGNOR T AMERICAN TELEPHONE AND TELEGRAPH COMPANY, A GORPORATION OF NEW YORK.

COMPOSITE SIGNALING-CIRCUITS.

' To all whom it may concern:

Be it knownthat I, HAROLD OsnonNE,

residing at New York, in the county of New York and fitate of New York, have invented 1 certain Improvements in Composite Signaling-Circuits, of which the following is a Y specification.

This invention relates to repeater circuits and more particularly to two-way, two repeater circuits associated with composited telephone and signaling lines. Its 0 ject is to protect the telephone repeater from signaling currents and to neutralize the effect of such currents upon the repeater.

The invention is best understood by refcrence'to the accompanying, drawing the figure of which constitutes a circuit diagram of the invention as applied to, a two-way two repeater'circuit.

'Referring to the drawing an incoming line L, .is connected to an. outgoing line L by means of a two-way repeater comprising repeater elements R and R For simplicity these elements are shown as of-the mechaniof repeater cal repeater type, but any other type such as, for instance, vacuum tube repeaters, may be used. Repeater element R has its input circuit 1 bridgedacross the mid-points of windings 2 and 3 of a three winding transformer,.

the winding 4 of which is in the output circuit 5 ofrepe'ater element R. In a similar manner the input circuit 6 ofrepeater element R is bridged across windings 7 and 8 of a three winding transformer whose third winding 9 is-in the output circuit 10 The lea hand terminals of windings 2 and 3 are coupled to the line L, through a transformer 11,- wh-ile the right hand terminals of said windings are similarly coupled througha transformer 12 to an artifical line N designed to balance line L,. :In a like manner the terminal windings 7 and 8 are coupled through transformers 13 and 14 to line L and artificial line N respectively.

In order that the conductors of the lines L and L niay be used for telegraphic or signaling purposes, a connection is made hetween the conductors of the lines and the artificial'lines, and leads extending to Morse or other signaling sets are tapped from these .connections. Thus conductor 15 of line L is connected to'c'onductor 17 of artificial line N by a connection vincludingimpedancecoil 18, contacts was 20 of jack 1 and plug P Specification of Letters Patent. Application filed June 8,

1917. Serial No. 173,528.

Patented Sept. 2, 1919.-

contacts 21 and 22 of-plug P and jack J an'd an inductance coil 23.

In a like manner conductor 24 of line L, is connected to conand-plug P contacts" andjack J and sets. The inductanccsl8, 23,26"and 31' are so proportioned-as to prevent high fre- -quency telephonecurrents flowing over line L, from being transmitted .to the Morse conductors 32 and 33, and alsoreduce the high frequency components of current which can flow from the telegraph or other signaling line to the telephone'line and repeater. At the same time these inductances permit of the passa e of low frequency signaling currents sue In order to prevent Morse impulses from being transmitted to the repeater element R a wave filter 34 is inserted between the line L and the induction coil 11. Said wave filter is a net-work comprising one or a plurality of sections, each section having a capacity in series with each side of the line,

'1 as Morse impulses.

and two serially connected inductances in shunt across the line, the common terminals of each an of ser ally connected 1nductances eing connected (to ground; The

properties of the wave filter are fully de scribed in U. S; patent application Serial No. 40,057 of G. A. Campbellwherein it is shown that a filter consisting of serial capacity and shunt inductance, transmits with V guishin all'currnts of frequency less than i said in erior limit. It-will be observed that filter 34 consists of two similar halves symmetrically related to ground and for this 1 reason the filter has been termed a duplex filter. The function of the filter 34: is twofold. First, it prevents low frequency signaling currents from entering the repeater apparatus while at the same time freely transmitting the relatively high frequency telephonic currents. Secondly, by virtue of its duplex structure and it prevents .the flow 0 signaling current ound connections,

from one side ofthe lineto the other, and

thus largely eliminates interference be-- 8, one-half of the energy in said circuit being transmitted. to line I1 through trans-- in line Li "tween composited signaling sets associated with the same telephone circuitq A second filter 35 in all respects similar to filter '34 is inserted between artificial line N and'induction coil l2 in order to balance the filter Should it be] desired to disconnect the Morse leads 32 and 33 from thelinje L plugs P and P ma be withdrawn,thereby per'- mittingthe springs, 19 22, and 30 torest upon their back contacts,.:.thereby associating apparatus 36, 37 38 and39 consisting of suitable inductances andicapacities with the line to simulate the Morse apparatus so as" not'to destroy thelbalance. The telegraphic" or signaling apparatusassociated with line L and artificial 'line' N is in all respects similar to that above described in connection. with line L andartificial line N 1 and hence need not be. further described.

The operation is as follows: Telephone currents from line L "are transmitted through filter 34 and transformer 11 t'o'tlie input circuit 1 of repeater R and are amplified by' the latter. The amplified currents in output circuit 10 induce-currents in the circuit including secondary windings 7 and former 13, the other half being transmitted "to artificial, line N through induction'coil 14. Input circuit 6 of repeater R5 is substantially unaffected by this energy as it is connected to points of equal potential with respect thereto. In a similar manner telephonic currents from line L arerepeated by repeater ,R to line L.

Telegraphic impulses from Morse 16ad32 divide at eontact 2l part of the current'flowing-over. contacts 20'.and,-19, through inductance 18 to line conductor 15, and the-other part-flowing over contacts'f21 and 22 and through inductance. 23 to conductor 17 leading to thezaltificial line-N v It has bee "proposed to reduce theefiect I of the telegraphprether signaling impulses by the use of series inductances and shunt condensersconstituting an; upper limiting filter in thetelegraph leg to --prevent the transmission of appreciable -high frequency components'of the telegraph current'to the telephone line, andtc;insert between the telephone lineand the telephone apparatus series condensers and "shunt inductances such as 34 in line L constituting a lower limit-- ing filter tosprevent the low frequency tele- .graph impulsesjfrom being transmitted to v the telephone apparatus; By means of this invention the apparatus required for this.- purpose, both in the telegraphbranches and in the telephone branch of the circuit, can

bereduced because the effect which would'lbe caused in the telephone repeater apparatus" is balanced by the neutralizing efi'ect induced through the artificial balancing circuit. This reduction in apparatus reduces the losses in and distortion of energy in both the telephone and telegraphcircuits.

Thus, in'the figure, inductance'coil 18 and 1 other apparatus. inserted inflconduc'tor 32 tends to prevent the high frequency components of the. Morse currents "fron beingv transmitted 1 to'conductor 15. and filter34 tends to prevent the low frequency signaling ,currentsfrom being transmitted to the pri-.

1nary of induction coilll, Such currents as are transmltted tojthe primary of induction lcoil 11,'h0 Wever, are balanced by the equal and opposite eflect of currents transmitted from conductor 32, through inductance coil the primary of induction coil 12. Therefore, filters 34 and35 inductance coils 18 and "'23 and other apparatus-associated with con ductorj 32 to reducethemagnitude of the 23 to conductor 17 and through filter 35 t .85 high frequency components of the currents can bedesigned to have a reduced effect on the transmission efliciency of the signaling currents and 'ofthe telephone currents. *They willthen have a-decreased eflectiveness in preventing the signaling current from reaching the. primaries of inductance co1ls -11 and 'l2 but the currents reaching their efi'ect-on the-telephone repeater.

Morse currents from conductor 33 are supplied to conductors '24 and 25 in a similar .manner and any currents passing from conductor 33 through the filters 34 and 35 induce opposing potentials with respect to the repeater. It will be seen, therefore, that the Morse currents are without; efiect on. the

signals on the telephone repeater, but in this case coil 23 'sho'uld be connected toconductor 25 and coil 31 to conductor'l'lg those two coils will neutralize each other in i f the telephone repeater be operated with r The artificial line N must be constructed I so as to balance with therecision desired the impedance of the meta ictelephone circuit L at ,all frequencies atwhichit isdesired to neutralize the effect of the signaling currents .on the telephone repeater by the balancing arrangement here described.v In

some cases, inorder to prevent-crossfire between conductors 17 and 25,,it may be desirable to construct artificial line N in two equal parts, .connected'in.'se1 'ies with a' ground connection at the'mid-point between i r 2 While the'invention has been'illustrated them.

as embodied in a certain specific form, it will be understood that it is capable of wide va-' riation without departing from the spirit of the appended claims; For example, ar-

rangement or a similar arrangement can be applied to types of telephone apparatus other than telephone frepeaters,such as terminal telephone sets, in cases in which theapparatus is connected" symmetrically between the line and a balancing artificial line.

What is claimed is:

. 1. In combination, a pair of line sections,- repeaters for interconnecting said line sections, artificiallines for balancing said line sections, signaling apparatus, a connectlon between said signaling apparatus and one of c .said lines, and a balancing connection from a said signaling apparatus to the corresponds ing artificial.1ine.--

2.:In combination, line sections for telephonic transmission, repeaters for interconnect ng sald line sectlons, artificial lines for balancing said line sections, signaling apparatus fora conductor of a line section, arallel branches extending from said si a ing apparatus, one of said branches lea ing to the line conductor, andthe other branch' leading to a conductor. of the corresponding signaling apparatus, a connectionfromfsai artificial line, and means to preventthef flow:

artificial line' so tha signaling currentsgin 2 said branch produce a reaction upon thejre-j peater equal and opposite to thatproduce'd by signaling currents inthe first branch 3. In combination, ;a tele hone transmls sion line, a 'balancingyartificial line therefor 1 of telephonic "currentover' said connections. i

In testimony whereof Ii -have signed; my a name -to this specification thi fourthday' of L45 June, 1917. I i i i a 

